1. Field of the Invention
The present invention relates to a slush mold for the improvement of the yield rate and the production efficiency of slush molding processes.
2. Description of the Prior Art
In a slush molding process, a resin material fed over the molding surface of a heated slush mold is melted into a molten resin film, and then the molten resin film is cooled to obtain a film-like molding. Surface coverings of the interior finishing parts of automotive vehicles are manufactured by slush molding.
FIGS. 8 and 9 illustrate a conventional slush mold 301 and a reservoir 101 for feeding a resin material to the slush mold 301. In a conventional slush molding process, the molding surface 311 of the slush mold 301 is heated by heating means such as heating oil pipes 321, and then a material S stored in the reservoir 101 is fed over the molding surface 311 by dropping naturally by virtue of gravity. Then the respective sealing surfaces 100 and 300 of the reservoir 101 and the slush mold 301 are joined flush. As illustrated in FIG. 9, the molding surface 311 is not formed over the entire inner surface of the slush mold 301; marginal surfaces E and F (not the part of the molding surface) are formed along the periphery of the molding surface 311. Since the reservoir 101 and the slush mold 301 are joined flush along the sealing surfaces 100 and 300, the material S fed from the reservoir 101 is distributed to the molding surface 311 as well as non-molding part of the marginal surfaces E and F, which wastes the material and reduces the yield rate of the slush molding. The configuration of the molding surface 311 relative to the inner surface of the slush mold 301 may be changed in order to improve the yield rate by reducing the amount of the material S that is fed over the marginal surfaces E and F. However, such a change of the configuration of the molding surface 311 is possible to make the drafting of the slush molding difficult or to deteriorate the distribution of the material to undercut portions in the molding surface 311. According to a known method of improving the yield rate, the marginal surfaces E and F are covered with heat insulating jackets 322 and inserts 323 to suppress the adhesion of the molten material over the surfaces of the inserts 323 corresponding to the marginal surfaces E' and F'. However, such a method is not enough to prevent the temperature increase at the inserts 323 and it lets the adhesion of the molten or half molten material to the surfaces of the inserts 323. The adhesion of the molten or half molten material to the surfaces of the inserts 323 requires additional time and labor for removing the molten material from the mold, and the half molten material is often mixed in the material stored in the reservoir 101, which deteriorates the stored material.